DD-WRT is a linux based open source firmware alternative for many different routers. You can check for device support at http://www.dd-wrt.ca/wiki/index.php/Supported_Devices. The main emphasis lies on providing the easiest possible handling while at the same time supporting a great number of functionalities within the framework of the respective hardware platform used.
DD-WRT gives much greater control and flexibility to your router. Their firmware definitely increases router performance, it also increases the resources available to whomever may be administrating the router. Graphs for bandwidth monitoring by day, month, and archived data, can provide you with accurate data so that you can track usage based internet, or to monitor who is using the most bandwidth within your home or office.
It provides much more flexibility and control over your routers current firmware. Blocking and restricting sites, Usage times, and NAT/QOS are much simpler to configure.
You can also access the wireless radio’s settings and increase or decrease the radio’s frequency to match your countries specifications.
There are so many more options and configurations that DD-WRT has to offer, and you can read more by visiting http://www.dd-wrt.ca
For the installation procedure based on your operating system please visit http://www.dd-wrt.ca/wiki/index.php/Tftp_flash